Cross-talk between notch and the estrogen receptor in breast cancer suggests novel therapeutic approaches

Innovating Cancer Treatment Through Cell Cycle, Telomerase, Angiogenesis, and Metastasis

Cancer remains a formidable challenge in the field of medicine, necessitating innovative therapeutic strategies to combat its relentless progression. The cell cycle, a tightly regulated process governing cell growth and division, plays a pivotal role in cancer development. Dysregulation of the cell cycle allows cancer cells to proliferate uncontrollably. Therapeutic interventions designed to disrupt the cell cycle offer promise in restraining tumor growth and progression. Telomerase, an enzyme responsible for maintaining telomere length, is often overactive in cancer cells, conferring them with immortality. Targeting telomerase presents an opportunity to limit the replicative potential of cancer cells and hinder tumor growth. Angiogenesis, the formation of new blood vessels, is essential for tumor growth and metastasis. Strategies aimed at inhibiting angiogenesis seek to deprive tumors of their vital blood supply, thereby impeding their progression. Metastasis, the spread of cancer cells from the primary tumor to distant sites, is a major challenge in cancer therapy. Research efforts are focused on understanding the underlying mechanisms of metastasis and developing interventions to disrupt this deadly process. This review provides a glimpse into the multifaceted approach to cancer therapy, addressing critical aspects of cancer biology-cell cycle regulation, telomerase activity, angiogenesis, and metastasis. Through ongoing research and innovative strategies, the field of oncology continues to advance, offering new hope for improved treatment outcomes and enhanced quality of life for cancer patients.

Targeting the crosstalk between estrogen receptors and membrane growth factor receptors in breast cancer treatment: Advances and opportunities

Estrogens play a critical role in the initiation and progression of breast cancer. Estrogen receptor (ER)α, ERβ, and G protein-coupled estrogen receptor are the primary receptors for estrogen in breast cancer. These receptors are mainly activated by binding with estrogens. The crosstalk between ERs and membrane growth factor receptors creates additional pathways that amplify the effects of their ligands and promote tumor growth. This crosstalk may cause endocrine therapy resistance in ERα-positive breast cancer. Furthermore, this may explain the resistance to anti-human epidermal growth factor receptor-2 (HER2) treatment in ERα-/HER2-positive breast cancer and chemotherapy resistance in triple-negative breast cancer. Accordingly, it is necessary to understand the complex crosstalk between ERs and growth factor receptors. In this review, we delineate the crosstalk between ERs and membrane growth factor receptors in breast cancer. Moreover, this review highlights the current progress in clinical treatment and discusses how pharmaceuticals target the crosstalk. Lastly, we discuss the current challenges and propose potential solutions regarding the implications of targeting crosstalk via pharmacological inhibition. Overall, the present review provides a landscape of the crosstalk between ERs and membrane growth factor receptors in breast cancer, along with valuable insights for future studies and clinical treatments using a chemotherapy-sparing regimen to improve patient quality of life.

Sex-specific outcomes in cancer therapy: the central role of hormones

Sex hormones play a pivotal role in modulating various physiological processes, with emerging evidence underscoring their influence on cancer progression and treatment outcomes. This review delves into the intricate relationship between sex hormones and cancer, elucidating the underlying biological mechanisms and their clinical implications. We explore the multifaceted roles of estrogen, androgens, and progesterone, highlighting their respective influence on specific cancers such as breast, ovarian, endometrial, and prostate. Special attention is given to estrogen receptor-positive (ER+) and estrogen receptor-negative (ER-) tumors, androgen receptor signaling, and the dual role of progesterone in both promoting and inhibiting cancer progression. Clinical observations reveal varied treatment responses contingent upon hormonal levels, with certain therapies like tamoxifen, aromatase inhibitors, and anti-androgens demonstrating notable success. However, disparities in treatment outcomes between males and females in hormone-sensitive cancers necessitate further exploration. Therapeutically, the utilization of hormone replacement therapy (HRT) during cancer treatments presents both potential risks and benefits. The promise of personalized therapies, tailored to an individual's hormonal profile, offers a novel approach to optimizing therapeutic outcomes. Concurrently, the burgeoning exploration of new drugs and interventions targeting hormonal pathways heralds a future of more effective and precise treatments for hormone-sensitive cancers. This review underscores the pressing need for a deeper understanding of sex hormones in cancer therapy and the ensuing implications for future therapeutic innovations.

Identification of a Notch transcriptomic signature for breast cancer

BACKGROUND

Dysregulated Notch signalling contributes to breast cancer development and progression, but validated tools to measure the level of Notch signalling in breast cancer subtypes and in response to systemic therapy are largely lacking. A transcriptomic signature of Notch signalling would be warranted, for example to monitor the effects of future Notch-targeting therapies and to learn whether altered Notch signalling is an off-target effect of current breast cancer therapies. In this report, we have established such a classifier.

METHODS

To generate the signature, we first identified Notch-regulated genes from six basal-like breast cancer cell lines subjected to elevated or reduced Notch signalling by culturing on immobilized Notch ligand Jagged1 or blockade of Notch by γ-secretase inhibitors, respectively. From this cadre of Notch-regulated genes, we developed candidate transcriptomic signatures that were trained on a breast cancer patient dataset (the TCGA-BRCA cohort) and a broader breast cancer cell line cohort and sought to validate in independent datasets.

RESULTS

An optimal 20-gene transcriptomic signature was selected. We validated the signature on two independent patient datasets (METABRIC and Oslo2), and it showed an improved coherence score and tumour specificity compared with previously published signatures. Furthermore, the signature score was particularly high for basal-like breast cancer, indicating an enhanced level of Notch signalling in this subtype. The signature score was increased after neoadjuvant treatment in the PROMIX and BEAUTY patient cohorts, and a lower signature score generally correlated with better clinical outcome.

CONCLUSIONS

The 20-gene transcriptional signature will be a valuable tool to evaluate the response of future Notch-targeting therapies for breast cancer, to learn about potential effects on Notch signalling from conventional breast cancer therapies and to better stratify patients for therapy considerations.

The role of estrogen receptors (ERs)-Notch pathway in thyroid toxicity induced by Di-2-ethylhexyl phthalate (DEHP) exposure: Population data and in vitro studies

BACKGROUND

This study aimed to assess the exposure level and risk of Di-2-ethylhexyl Phthalate (DEHP) among adults in Jilin Province, China, clarify the impact of DEHP on human thyroid function, and to explore the role of estrogen receptors (ERs)-Notch signaling pathway in the effect of DEHP metabolites on thyroid hormones based on population data and in vitro experiments.

METHODS

312 adults participated in this study. Urinary DEHP metabolites were determined by high performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS). Two pharmacokinetic models were used to evaluate the estimated daily intake (EDI) and hazard quotient (HQ) of the adults. Multiple linear regression and mediating effect models were used to evaluate the target associations. In cell experiments, thyroid follicular epithelial (Nthy-ori3-1) cells were exposed to mono (2-ethylhexyl) phthalate (MEHP) for testing. The inhibitions of ERα and Notch pathway were conducted by siRNA and Notch pathway inhibitor DAPT.

RESULTS

The detection rate of five DEHP metabolites was 97.1∼100.0%. The HQ value of 0.3% of adults was higher than 1. The levels of urinary DEHP metabolites were significantly correlated with thyrotropin (TSH), thyrotropin-releasing hormone (TRH), total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3) and free thyroxine (FT4) and gene (estrogen receptor α (ERα), Notch1, Dll4) levels. The ERα-Notch pathway played a mediating role in the association between DEHP metabolite levels and FT4. The cell results showed, the levels of FT3 and FT4 in cell supernatant decreased after MEHP exposure, and the downward trend was reversed after ERα and notch pathways were inhibited, notch pathway genes also decreased after ERα inhibition.

CONCLUSION

Adults in the Jilin Province of China were widely exposed to DEHP. ERs-Notch pathway played an important role in the effect of DEHP metabolites on thyroid hormones.

Regulation of the Notch signaling pathway by natural products for cancer therapy

The Notch signaling pathway is an evolutionarily conserved pathway that modulates normal biological processes involved in cellular differentiation, apoptosis, and stem cell self-renewal in a context-dependent fashion. Attributed to its pleiotropic physiological roles, both overexpression and silencing of the pathway are associated with the emergence, progression, and poorer prognosis in various types of cancer. To decrease disease incidence and promote survival, targeting Notch may have chemopreventive and anti-cancer effects. Natural products with profound historical origins have distinguished themselves from other therapies due to their easy access, high biological compatibility, low toxicity, and reliable effects at specific physiological sites in vivo. This review describes the Notch signaling pathway, particularly its normal activation process, and some main illnesses related to Notch signaling pathway dysregulation. Emphasis is placed on the effects and mechanisms of natural products targeting the Notch signaling pathway in diverse cancer types, including curcumin, ellagic acid (EA), resveratrol, genistein, epigallocatechin-3-gallate (EGCG), quercetin, and xanthohumol and so on. Existing evidence indicates that natural products are feasible solution to fight against cancer by targeting Notch signaling, either alone or in combination with current therapeutic agents.

Cell aggregation activates small GTPase Rac1 and induces CD44 cleavage by maintaining lipid raft integrity

Lipid rafts are highly ordered membrane domains that are enriched in cholesterol and glycosphingolipids and serve as major platforms for signal transduction. Cell detachment from the extracellular matrix (ECM) triggers lipid raft disruption and anoikis, which is a barrier for cancer cells to metastasize. Compared to single circulating tumor cells (CTCs), our recent studies have demonstrated that CD44-mediatd cell aggregation enhances the stemness, survival and metastatic ability of aggregated cells. Here, we investigated whether and how lipid rafts are involved in CD44-mediated cell aggregation. We found that cell detachment, which mimics the condition when tumor cells detach from the ECM to metastasize, induced lipid raft disruption in single cells, but lipid raft integrity was maintained in aggregated cells. We further found that lipid raft integrity in aggregated cells was required for Rac1 activation to prevent anoikis. In addition, CD44 and γ-secretase coexisted at lipid rafts in aggregated cells, which promoted CD44 cleavage and generated CD44 intracellular domain (CD44 ICD) to enhance stemness of aggregated cells. Consequently, lipid raft disruption inhibited Rac1 activation, CD44 ICD generation, and metastasis. Our findings reveal two new pathways regulated by CD44-mediated cell aggregation via maintaining lipid raft integrity. These findings also suggest that targeting cell aggregation-mediated pathways could be a novel therapeutic strategy to prevent CTC cluster-initiated metastasis.

The Efficacy of CB-103, a First-in-Class Transcriptional Notch Inhibitor, in Preclinical Models of Breast Cancer

BACKGROUND

The efficacy of CB-103 was evaluated in preclinical models of both ER+ and TNBC. Furthermore, the therapeutic efficacy of combining CB-103 with fulvestrant in ER+ BC and paclitaxel in TNBC was determined.

METHODS

CB-103 was screened in combination with a panel of anti-neoplastic drugs. We evaluated the anti-tumor activity of CB-103 with fulvestrant in ESR1-mutant (Y537S), endocrine-resistant BC xenografts. In the same model, we examined anti-CSC activity in mammosphere formation assays for CB-103 alone or in combination with fulvestrant or palbociclib. We also evaluated the effect of CB-103 plus paclitaxel on primary tumors and CSC in a GSI-resistant TNBC model HCC1187. Comparisons between groups were performed with a two-sided unpaired Students' t-test. A one-way or two-way ANOVA followed by Tukey's post-analysis was performed to analyze the in vivo efficacy study results.

THE RESULTS

CB-103 showed synergism with fulvestrant in ER+ cells and paclitaxel in TNBC cells. CB-103 combined with fulvestrant or paclitaxel potently inhibited mammosphere formation in both models. Combination of CB-103 and fulvestrant significantly reduced tumor volume in an ESR1-mutant, the endocrine-resistant BC model. In a GSI-resistant TNBC model, CB-103 plus paclitaxel significantly delayed tumor growth compared to paclitaxel alone.

CONCLUSION

our data indicate that CB-103 is an attractive candidate for clinical investigation in endocrine-resistant, recurrent breast cancers with biomarker-confirmed Notch activity in combination with SERDs and/or CDKis and in TNBCs with biomarker-confirmed Notch activity in combination with taxane-containing chemotherapy regimens.

Novel insights into DNA methylation-based epigenetic regulation of breast tumor angiogenesis

Breast tumors are highly vascularized and dependent on angiogenesis for growth, progression and metastasis. Like other solid tumors, vasculature in breast tumors also display leaky and tortuous phenotype and hence inhibit immune cell infiltration, show reduced efficacy to anticancer drugs and radiotherapy. Epigenetic reprogramming including significant alterations in DNA methylation in tumor and stromal cells generate an imbalance in expression of pro- and anti-angiogenic factors and subsequently lead to disordered angiogenesis. Hence, understanding DNA methylation-based regulation of angiogenesis in breast tumors may open new avenues for designing therapeutic targets. Our present review manuscript summarized contemporary knowledge of influence of DNA methylation in regulating angiogenesis. Further, we identified novel set of pro-angiogenic genes enriched in endothelial cells which are coregulated with DNMT isoforms in breast tumors and harboring CpG islands. Our analysis revealed promoters of pro-angiogenic genes were hypomethylated and anti-angiogenic genes were hypermethylated in tumors and further reflected on their expression patterns. Interestingly, promoter DNA methylation intensities of novel set of pro-angiogenic genes significantly correlated to patient survival outcome.

An Update on Tamoxifen and the Chemo-Preventive Potential of Vitamin E in Breast Cancer Management

Breast cancer (BC) is the most common female cancer in terms of incidence and mortality worldwide. Tamoxifen (Nolvadex) is a widely prescribed, oral anti-estrogen drug for the hormonal treatment of estrogen-receptor-positive BC, which represents 70% of all BC subtypes. This review assesses the current knowledge on the molecular pharmacology of tamoxifen in terms of its anticancer and chemo-preventive actions. Due to the importance of vitamin E compounds, which are widely taken as a supplementary dietary component, the review focuses only on the potential importance of vitamin E in BC chemo-prevention. The chemo-preventive and onco-protective effects of tamoxifen combined with the potential effects of vitamin E can alter the anticancer actions of tamoxifen. Therefore, methods involving an individually designed, nutritional intervention for patients with BC warrant further consideration. These data are of great importance for tamoxifen chemo-prevention strategies in future epidemiological studies.

Inorganic nanoparticle-based advanced cancer therapies: promising combination strategies

Inorganic nanoparticles for drug delivery in cancer treatment offer many potential advantages because they can maximize therapeutic effect through targeting ligands while minimizing off-target side-effects through drug adsorption and infiltration. Although inorganic nanoparticles were introduced as drug carriers, they have emerged as having the capacity for combined therapeutic capabilities, including anticancer effects through cytotoxicity, suppression of oncogenes and cancer cell signaling pathway inhibition. The most promising advanced strategies for cancer therapy are as synergistic platforms for RNA interference (siRNA, miRNA, shRNA) and as synergistic drug delivery agents for the inhibition of cancer cell signaling pathways. The present work summarizes relevant current work, the promise of which is suggested by a projected compound annual growth rate of ∼20% for drug delivery alone.

Herbal Ingredients in the Prevention of Breast Cancer: Comprehensive Review of Potential Molecular Targets and Role of Natural Products

Among various cancers, breast cancer is the most prevalent type in women throughout the world. Breast cancer treatment is challenging due to complex nature of the etiology of disease. Cell division cycle alterations are often encountered in a variety of cancer types including breast cancer. Common treatments include chemotherapy, surgery, radiotherapy, and hormonal therapy; however, adverse effects and multidrug resistance lead to complications and noncompliance. Accordingly, there is an increasing demand for natural products from medicinal plants and foods. This review summarizes molecular mechanisms of signaling pathways in breast cancer and identifies mechanisms by which natural compounds may exert their efficacy in the treatment of breast cancer.

Breast cancer: molecular mechanisms of underlying resistance and therapeutic approaches

Breast cancer (BC) affects over 250,000 women in the US each year. Drug-resistant cancer cells are responsible for most breast cancer fatalities. Scientists are developing novel chemotherapeutic drugs and targeted therapy combinations to overcome cancer cell resistance. Combining drugs can reduce the chances of a tumor developing resistance to treatment. Clinical research has shown that combination chemotherapy enhances or improves survival, depending on the patient's response to treatment. Combination therapy is a highly successful supplemental cancer treatment. This review sheds light on intrinsic resistance to BC drugs and the importance of combination therapy for BC treatment. In addition to recurrence and metastasis of BC, the article discussed biomarkers for BC.

Breast Cancer Metastasis: Mechanisms and Therapeutic Implications

Breast cancer is the most common malignancy in women worldwide. Metastasis is the leading cause of high mortality in most cancers. Although predicting the early stage of breast cancer before metastasis can increase the survival rate, breast cancer is often discovered or diagnosed after metastasis has occurred. In general, breast cancer has a poor prognosis because it starts as a local disease and can spread to lymph nodes or distant organs, contributing to a significant impediment in breast cancer treatment. Metastatic breast cancer cells acquire aggressive characteristics from the tumor microenvironment (TME) through several mechanisms including epithelial–mesenchymal transition (EMT) and epigenetic regulation. Therefore, understanding the nature and mechanism of breast cancer metastasis can facilitate the development of targeted therapeutics focused on metastasis. This review discusses the mechanisms leading to metastasis and the current therapies to improve the early diagnosis and prognosis in patients with metastatic breast cancer.

Notch Signaling in Breast Tumor Microenvironment as Mediator of Drug Resistance

Notch signaling dysregulation encourages breast cancer progression through different mechanisms such as stem cell maintenance, cell proliferation and migration/invasion. Furthermore, Notch is a crucial driver regulating juxtracrine and paracrine communications between tumor and stroma. The complex interplay between the abnormal Notch pathway orchestrating the activation of other signals and cellular heterogeneity contribute towards remodeling of the tumor microenvironment. These changes, together with tumor evolution and treatment pressure, drive breast cancer drug resistance. Preclinical studies have shown that targeting the Notch pathway can prevent or reverse resistance, reducing or eliminating breast cancer stem cells. In the present review, we will summarize the current scientific evidence that highlights the involvement of Notch activation within the breast tumor microenvironment, angiogenesis, extracellular matrix remodeling, and tumor/stroma/immune system interplay and its involvement in mechanisms of therapy resistance.

Roles of Notch Signaling in the Tumor Microenvironment

The Notch signaling pathway is an architecturally simple signaling mechanism, well known for its role in cell fate regulation during organ development and in tissue homeostasis. In keeping with its importance for normal development, dysregulation of Notch signaling is increasingly associated with different types of tumors, and proteins in the Notch signaling pathway can act as oncogenes or tumor suppressors, depending on the cellular context and tumor type. In addition to a role as a driver of tumor initiation and progression in the tumor cells carrying oncogenic mutations, it is an emerging realization that Notch signaling also plays a role in non-mutated cells in the tumor microenvironment. In this review, we discuss how aberrant Notch signaling can affect three types of cells in the tumor stroma-cancer-associated fibroblasts, immune cells and vascular cells-and how this influences their interactions with the tumor cells. Insights into the roles of Notch in cells of the tumor environment and the impact on tumor-stroma interactions will lead to a deeper understanding of Notch signaling in cancer and inspire new strategies for Notch-based tumor therapy.

Notch controls the cell cycle to define leader versus follower identities during collective cell migration

Coordination of cell proliferation and migration is fundamental for life, and its dysregulation has catastrophic consequences, such as cancer. How cell cycle progression affects migration, and vice versa, remains largely unknown. We address these questions by combining in silico modelling and in vivo experimentation in the zebrafish trunk neural crest (TNC). TNC migrate collectively, forming chains with a leader cell directing the movement of trailing followers. We show that the acquisition of migratory identity is autonomously controlled by Notch signalling in TNC. High Notch activity defines leaders, while low Notch determines followers. Moreover, cell cycle progression is required for TNC migration and is regulated by Notch. Cells with low Notch activity stay longer in G1 and become followers, while leaders with high Notch activity quickly undergo G1/S transition and remain in S-phase longer. In conclusion, TNC migratory identities are defined through the interaction of Notch signalling and cell cycle progression.

Emerging treatment strategies for metastatic triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a heterogeneous subtype of breast cancer that is often associated with an aggressive phenotype and a poor prognosis. Cytotoxic chemotherapy remains the mainstay of treatment for most patients with metastatic TNBC (mTNBC), but duration of response is often short and median overall survival is only 12–18 months. Therefore, it is critical to identify novel treatment strategies to improve outcomes for these patients. In this review article, we discuss recent advances in treatment strategies for patients with mTNBC including the use of immune checkpoint inhibitors, targeted therapies, and antibody–drug conjugates. For each topic, we summarize important preclinical and clinical data, discuss implications for clinical practice, and highlight future research directions.

GIT1 protects against breast cancer growth through negative regulation of Notch

Hyperactive Notch signalling is frequently observed in breast cancer and correlates with poor prognosis. However, relatively few mutations in the core Notch signalling pathway have been identified in breast cancer, suggesting that as yet unknown mechanisms increase Notch activity. Here we show that increased expression levels of GIT1 correlate with high relapse-free survival in oestrogen receptor-negative (ER(-)) breast cancer patients and that GIT1 mediates negative regulation of Notch. GIT1 knockdown in ER(-) breast tumour cells increased signalling downstream of Notch and activity of aldehyde dehydrogenase, a predictor of poor clinical outcome. GIT1 interacts with the Notch intracellular domain (ICD) and influences signalling by inhibiting the cytoplasm-to-nucleus transport of the Notch ICD. In xenograft experiments, overexpression of GIT1 in ER(-) cells prevented or reduced Notch-driven tumour formation. These results identify GIT1 as a modulator of Notch signalling and a guardian against breast cancer growth.

Notch signalling is reported to be hyperactivated in oestrogen receptor-negative (ER-) breast cancer. Here the authors show that G protein-coupled receptor kinase-interacting protein 1 (GIT1) negatively regulates Notch signalling and tumour growth in ER- breast cancer by blocking Notch ICD nuclear translocation.

A Phase Ib Dose Escalation Trial of RO4929097 (a γ-secretase inhibitor) in Combination with Exemestane in Patients with ER + Metastatic Breast Cancer (MBC)

PRECLINICAL STUDIES: have demonstrated a complex cross-talk between Notch and estrogen signaling in ERα-positive breast cancer. Gamma-secretase inhibitors (GSIs) are investigational agents that block the cleavage and activation of Notch receptors. In animal models of endocrine-resistant breast cancer, combinations of tamoxifen and GSIs produce additive or synergistic efficacy, while decreasing the intestinal toxicity of GSIs. However, results of a clinical trial of a GSI-endocrine therapy combination in the metastatic setting have not been published to date, nor had the safety of such combinations been investigated with longer term treatment. We conducted a phase 1b dose escalation trial (NCT01149356) of GSI RO4929097 with exemestane in patients with ERα+, metastatic breast cancer (MBC) STUDY OBJECTIVES: To determine the safety, tolerability and maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) of RO4929097 when administered in combination with exemestane in patients with estrogen receptor positive metastatic breast cancer RESULTS: We enrolled 15 patients with MBC. Of 14 evaluable patients, one had a partial response, 6 had stable disease and 7 progressive disease. Twenty % of patients had stable disease for ≥ 6 months. Common toxicities included nausea (73.3%), anorexia (60%), hyperglycemia (53.3%), hypophosphatemia (46.7%), fatigue (66.7%) and cough (33.0%). Grade 3 toxicities were uncommon, and included hypophosphatemia (13%) and rash (6.3%). Rash was the only DLT observed at 140 mg/d. Results suggest a possible recommended phase 2 dose of 90 mg/d. Ten patients with evaluable archival tissue showed expression of PKCα, which correlated with expression of Notch4. Mammospheres from a PKCα-expressing, endocrine-resistant T47D cell line were inhibited by a GSI-fulvestrant combination CONCLUSIONS: Our data indicate that combinations including endocrine therapy and Notch inhibitors deserve further investigation in endocrine-resistant ERα-positive breast cancer.

Analyzing the Interaction of RBPJ with Mitotic Chromatin and Its Impact on Transcription Reactivation upon Mitotic Exit

The sequence-specific transcription factor RBPJ, also known as CSL (CBF1, Su(H), Lag1), is an evolutionarily conserved protein that mediates Notch signaling to guide cell fates. When cells enter mitosis, DNA is condensed and most transcription factors dissociate from chromatin; however, a few, select transcription factors, termed bookmarking factors, remain associated. These mitotic chromatin-bound factors are believed to play important roles in maintaining cell fates through cell division. RBPJ is one such factor that remains mitotic chromatin associated and therefore could function as a bookmarking factor. Here, we describe how to obtain highly purified mitotic cells from the mouse embryonal carcinoma cell line F9, perform chromatin immunoprecipitation with mitotic cells, and measure the first run of RNA synthesis upon mitotic exit. These methods serve as basis to understand the roles of mitotic bookmarking by RBPJ in propagating Notch signals through cell division.

Novel doxorubicin / folate-targeted trans-ferulic acid-loaded PLGA nanoparticles combination: In-vivo superiority over standard chemotherapeutic regimen for breast cancer treatment

AIM

Doxorubicin/Cyclophosphamide (AC) is one of the standard adjuvant anthracycline-containing regimens that is still in use for breast cancer treatment. Cancer cell resistance and AC-induced side effects make treatment suboptimal and worsen patients' quality of life. This study aimed to improve trans-ferulic acid's (TFA) efficiency via loading into folate-receptor-targeted-poly lactic-co-glycolic acid nanoparticles (FA-PLGA-TFA NPs). Also, investigating both the antitumor efficacy of Doxorubicin (Dox)/FA-PLGA-TFA NPs combination against dimethylbenz[a]anthracene (DMBA)-induced breast cancer and its safety profile.

METHODS

FA-PLGA-TFA NPs were optimally fabricated and characterized. Levels of Notch1, Hes1, Wnt-3a, β-catenin, MMP-9, cyclin D1, Permeability-Glycoprotein (P-gp), ERα, PR, and HER2 were assessed as a measure of the antitumor efficacy of different treatment protocols. Histopathological examination of heart and bone, levels of ALT, AST, ALP, CK-MB, and WBCs count were evaluated to ensure the combination's safety profile.

KEY FINDINGS

Dox/FA-PLGA-TFA NPs not only inhibited Notch signaling but also suppressed Notch synergy with Wnt, estrogen, progesterone, and HER2 pathways. Interestingly, Dox/FA-PLGA-TFA NPs decreased P-gp level and preserved heart, bone, and liver health as well as WBCs count.

SIGNIFICANCE

Dox/FA-PLGA-TFA NPs reduced the side-effects of each single drug, and at the same time exerted excellent antitumor activity that surpass the AC regimen in evading cancer cell resistance and having a superior safety profile.

Nuclear Mechanisms Involved in Endocrine Resistance

Endocrine therapy is a standard treatment offered to patients with ERα (estrogen receptor α)-positive breast cancer. In endocrine therapy, ERα is either directly targeted by anti-estrogens or indirectly by aromatase inhibitors which cause estrogen deficiency. Resistance to these drugs (endocrine resistance) compromises the efficiency of this treatment and requires additional measures. Endocrine resistance is often caused by deregulation of the PI3K/AKT/mTOR pathway and/or cyclin-dependent kinase 4 and 6 activities allowing inhibitors of these factors to be used clinically to counteract endocrine resistance. The nuclear mechanisms involved in endocrine resistance are beginning to emerge. Exploring these mechanisms may reveal additional druggable targets, which could help to further improve patients' outcome in an endocrine resistance setting. This review intends to summarize our current knowledge on the nuclear mechanisms linked to endocrine resistance.

Mammary Development and Breast Cancer: a Notch Perspective

Mammary gland development primarily occurs postnatally, and this unique process is complex and regulated by systemic hormones and local growth factors. The mammary gland is also a highly dynamic organ that undergoes profound changes at puberty and during the reproductive cycle. These changes are driven by mammary stem cells (MaSCs). Breast cancer is one of the most common causes of cancer-related death in women. Cancer stem cells (CSCs) play prominent roles in tumor initiation, drug resistance, tumor recurrence, and metastasis. The highly conserved Notch signaling pathway functions as a key regulator of the niche mediating mammary organogenesis and breast neoplasia. In this review, we discuss mechanisms by which Notch contributes to breast carcinoma pathology and suggest potentials for therapeutic targeting of Notch in breast cancer. In summary, we provide a comprehensive overview of Notch functions in regulating MaSCs, mammary development, and breast cancer.

Molecular Mechanisms Underlying the Anti-Breast Cancer Stem Cell Activity of Pterocladia capillacea and Corallina officinalis Polysaccharides

OBJECTIVE

This study aimed to appraise the activity of Pterocladia capillacea and Corallina officinalis polysaccharides against breast cancer stem cells (BCSCs). P. capillacea and C. officinalis polysaccharides were characterized to be sulfated polysaccharide-protein complexes.

METHODS

Cytotoxicity of the polysaccharides against MDA-MB-231 and MCF-7 cell lines along with their impact on CD44+/CD24- and aldehyde dehydrogenase 1(ALDH1) positive BCSC population were determined. Their effect on gene expression of CSC markers, Wnt/β-catenin and Notch signaling pathways was evaluated.

RESULTS

P. capillacea and C. officinalis polysaccharides inhibited the growth of breast cancer cells and reduced BCSC subpopulation. P. capillacea polysaccharides significantly down-regulated OCT4, SOX2, ALDH1A3 and vimentin in MDA-MB-231 as well as in MCF-7 cells except for vimentin that was up-regulated in MCF-7 cells. C. officinalis polysaccharides exhibited similar effects except for OCT4 that was up-regulated in MDA-MB-231 cells. Significant suppression of Cyclin D1 gene expression was noted in MDA-MB-231 and MCF-7 cells treated with P. capillacea or C. officinalis polysaccharides. β-catenin and c-Myc genes were significantly down-regulated in MDA-MB-231 cells treated with C. officinalis and P. capillacea polysaccharides, respectively, while being up-regulated in MCF-7 cells treated with either of them. Additionally, P. capillacea and C. officinalis polysaccharides significantly down-regulated Hes1 gene in MCF-7 cells despite increasing Notch1 gene expression level. However, significant down-regulation of Notch1 gene was observed in MDA-MB-231 cells treated with P. capillacea polysaccharides.

CONCLUSION

Collectively, this study provides evidence for the effectiveness of P. capillacea and C. officinalis polysaccharides in targeting BCSCs through interfering with substantial signaling pathways contributing to their functionality.

Notch Signalling in Breast Development and Cancer

The Notch signalling pathway is a highly conserved developmental signalling pathway, with vital roles in determining cell fate during embryonic development and tissue homeostasis. Aberrant Notch signalling has been implicated in many disease pathologies, including cancer. In this review, we will outline the mechanism and regulation of the Notch signalling pathway. We will also outline the role Notch signalling plays in normal mammary gland development and how Notch signalling is implicated in breast cancer tumorigenesis and progression. We will cover how Notch signalling controls several different hallmarks of cancer within epithelial cells with sections focussed on its roles in proliferation, apoptosis, invasion, and metastasis. We will provide evidence for Notch signalling in the breast cancer stem cell phenotype, which also has implications for therapy resistance and disease relapse in breast cancer patients. Finally, we will summarise the developments in therapeutic targeting of Notch signalling, and the pros and cons of this approach for the treatment of breast cancer.

NOTCH signaling: Journey of an evolutionarily conserved pathway in driving tumor progression and its modulation as a therapeutic target

Notch signaling, an evolutionarily conserved signaling cascade, is critical for normal biological processes of cell differentiation, development, and homeostasis. Deregulation of the Notch signaling pathway has been associated with tumor progression. Thus, Notch presents as an interesting target for a variety of cancer subtypes and its signaling mechanisms have been actively explored from the therapeutic viewpoint. However, besides acting as an oncogene, Notch pathway can possess also tumor suppressive functions, being implicated in inhibition of cancer development. Given such interesting dual and dynamic role of Notch, in this review, we discuss how the evolutionarily conserved Notch signaling pathway drives hallmarks of tumor progression and how it could be targeted for a promising treatment and management of cancer. In addition, the up-to-date information on the inhibitors currently under clinical trials for Notch targets is presented along with how NOTCH inhibitors can be used in conjunction with established chemotherapy/radiotherapy regimes.

Estrogen receptor-α signaling in post-natal mammary development and breast cancers

17β-estradiol controls post-natal mammary gland development and exerts its effects through Estrogen Receptor ERα, a member of the nuclear receptor family. ERα is also critical for breast cancer progression and remains a central therapeutic target for hormone-dependent breast cancers. In this review, we summarize the current understanding of the complex ERα signaling pathways that involve either classical nuclear “genomic” or membrane “non-genomic” actions and regulate in concert with other hormones the different stages of mammary development. We describe the cellular and molecular features of the luminal cell lineage expressing ERα and provide an overview of the transgenic mouse models impacting ERα signaling, highlighting the pivotal role of ERα in mammary gland morphogenesis and function and its implication in the tumorigenic processes. Finally, we describe the main features of the ERα-positive luminal breast cancers and their modeling in mice.

Role of m6A methyltransferase component VIRMA in multiple human cancers (Review)

N6-Methyladenosine (m6A) modification is one of the most widely distributed RNA modifications in eukaryotes. It participates in various RNA functions and plays vital roles in tissue development, stem cell formation and differentiation, heat shock response control, and circadian clock controlling, particularly during tumor development. The reversible regulation of m6A modification is affected by the so-called ‘reader’, ‘writer’ and ‘eraser’. As a required component and the largest methyltransferase, vir-like m6A methyltransferase associated (VIRMA) can promote the progression of cancer and is associated with poor survival in multiple types of cancer. The present review investigated the role of VIRMA in various types of cancer. In an m6A-dependent or -independent manner, VIRMA can play an oncogenic role by regulating cancer cell proliferation, migration and invasion, metastasis, apoptosis resistance and tumor growth in different pathways by targeting stem factors, CCAT1/2, ID2, GATA3, CDK1, c-Jun, etc. VIRMA can also predict better prognosis in kidney renal clear cell carcinoma (KIRC), kidney renal papillary cell carcinoma (KIRP) and papillary thyroid carcinoma by TCGA analysis. The obvious oncogenic roles of VIRMA observed in different types of cancer and the mechanisms of VIRMA promoting cancers provided the basis for potential therapeutic targeting for cancer treatments.

Nitric oxide-targeted therapy inhibits stemness and increases the efficacy of tamoxifen in estrogen receptor-positive breast cancer cells

Cancer stem cells (CSCs) are involved in the resistance of estrogen (ER)-positive breast tumors against endocrine therapy. On the other hand, nitric oxide (NO) plays a relevant role in CSC biology, although there are no studies addressing how this important signaling molecule may contribute to resistance to antihormonal therapy in ER+ breast cancer. Therefore, we explored whether targeting NO in ER+ breast cancer cells impacts CSC subpopulation and sensitivity to hormonal therapy with tamoxifen. NO was targeted in ER+ breast cancer cells by specific NO depletion and NOS2 silencing and mammosphere formation capacity, stem cell markers and tamoxifen sensitivity were analyzed. An orthotopic breast tumor model in mice was also performed to analyze the efficacy of NO-targeted therapy plus tamoxifen. Kaplan-Meier curves were made to analyze the association of NOS2 gene expression with survival of ER+ breast cancer patients treated with tamoxifen. Our results show that targeting NO inhibited mamosphere formation, CSC markers expression and increased the antitumoral efficacy of tamoxifen in ER+ breast cancer cells, whereas tamoxifen-resistant cells displayed higher expression levels of NOS2 and Notch-1 compared with parental cells. Notably, NO-targeted therapy plus tamoxifen was more effective than either treatment alone in an orthotopic breast tumor model in immunodeficient mice. Furthermore, low NOS2 expression was significantly associated with a higher metastasis-free survival in ER+ breast cancer patients treated with tamoxifen. In conclusion, our data support that NO-targeted therapy in ER+ breast cancer may contribute to increase the efficacy of antihormonal therapy avoiding the development of resistance to these treatments.

Metformin Induces Apoptosis and Inhibits Notch1 in Malignant Pleural Mesothelioma Cells

Malignant pleural mesothelioma (MPM) is an aggressive asbestos-related cancer arising from the mesothelial cells lining the pleural cavity. MPM is characterized by a silent clinical progression and a highly resistance to conventional chemo/radio-therapies. MPM patients die in a few months/years from diagnosis. Notch signaling is a well-conserved cell communication system, which regulates many biological processes. In humans, the dysregulation of Notch pathway potentially contributes to cancer onset/progression, including MPM. Metformin is the first-line drug used to treat type 2 diabetes mellitus. Metformin is proven to be an effective antitumor drug in preclinical models of different types of cancer. To date, clinical efficacy is being studied in many clinical trials. In this study, the anti-proliferative effect of metformin on MPM cells and the putative involvement of Notch1 as a mediator of metformin activities, were investigated. MPM cells showed high levels of Notch1 activation compared to normal pleural mesothelial cells. Furthermore, metformin treatment hampered MPM cell proliferation and enhanced the apoptotic process, accompanied by decreased Notch1 activation.

Breast Cancer Stem Cells: Biomarkers, Identification and Isolation Methods, Regulating Mechanisms, Cellular Origin, and Beyond

Despite recent advances in diagnosis and treatment, breast cancer (BC) is still a major cause of cancer-related mortality in women. Breast cancer stem cells (BCSCs) are a small but significant subpopulation of heterogeneous breast cancer cells demonstrating strong self-renewal and proliferation properties. Accumulating evidence has proved that BCSCs are the driving force behind BC tumor initiation, progression, metastasis, drug resistance, and recurrence. As a heterogeneous disease, BC contains a full spectrum of different BC subtypes, and different subtypes of BC further exhibit distinct subtypes and proportions of BCSCs, which correspond to different treatment responses and disease-specific outcomes. This review summarized the current knowledge of BCSC biomarkers and their clinical relevance, the methods for the identification and isolation of BCSCs, and the mechanisms regulating BCSCs. We also discussed the cellular origin of BCSCs and the current advances in single-cell lineage tracing and transcriptomics and their potential in identifying the origin and lineage development of BCSCs.

The clinical significance of Notch1 immunoexpression in Caucasian patients with colorectal adenocarcinoma

Introduction

Colorectal cancer (CRC) is traditionally regarded as the most commonly diagnosed gastrointestinal malignant disease. Nevertheless, despite advances in diagnosis and novel therapeutic options, the clinical outcomes of patients are still not satisfactory.

Aim

To investigate the clinicopathological and prognostic roles of Notch1 expression, the immunohistochemical investigation was performed in samples of CRC tumour tissues, adjacent non-pathological mucosa, and metastatic foci in regional lymph nodes in Caucasian patients.

Material and methods

Paraffin-embedded adenocarcinoma samples were assessed immunohistochemically for Notch1 protein and scored according to the percentage of cells with a positive reaction combined with staining intensity. Connections between Notch1 immunoexpression and clinicopathological factors including the 5-year overall survival (OS) were evaluated.

Results

The level of the Notch1 immunohistochemical reactivity was correlated with the grade of the histological differentiation, size of the primary tumour, regional lymph node involvement, and perineural invasion (all p < 0.001). Kaplan-Meier survival analysis showed that the survival time for patients with a low expression of Notch1 was significantly longer than that for patients with moderate or strong level of Notch1 immunoreactivity (p < 0.001).

Conclusions

The enhanced level of Notch1 immunoexpression was significantly associated with malignancy-related clinicopathological factors and reduced the 5-year overall survival in CRC patients.

ASR490, a Small Molecule, Overrides Aberrant Expression of Notch1 in Colorectal Cancer

Notch1 activation triggers significant oncogenic signaling that manifests as enhanced metastatic potential and tumorigenesis in colorectal cancer. Novel small-molecule inhibitors, mainly plant-derived analogs, have low toxicity profiles and higher bioavailability. In this study, we have developed a small molecule, ASR490, by modifying structure of naturally occurring compound Withaferin A. ASR490 showed a growth-inhibitory potential by downregulating Notch1 signaling in HCT116 and SW620 cell lines. Docking studies and thermal shift assays confirmed that ASR490 binds to Notch1, whereas no changes in Notch2 and Notch3 expression were seen in colorectal cancer cells. Notch1 governs epithelial-to-mesenchymal transition signaling and is responsible for metastasis, which was abolished by ASR490 treatment. To further confirm the therapeutic potential of ASR490, we stably overexpressed Notch1 in HCT-116 cells and determined its inhibitory potential in transfected colorectal cancer (Notch1/HCT116) cells. ASR490 effectively prevented cell growth in both the vector (P = 0.005) and Notch1 (P = 0.05) transfectants. The downregulation of Notch1 signaling was evident, which corresponded with downregulation of mesenchymal markers, including N-cadherin and β-catenin and induction of E-cadherin in HCT-116 transfectants. Intraperitoneal administration of a 1% MTD dose of ASR490 (5 mg/kg) effectively suppressed the tumor growth in control (pCMV/HCT116) and Notch1/HCT116 in xenotransplanted mice. In addition, downregulation of Notch1 and survival signaling in ASR-treated tumors confirmed the in vitro results. In conclusion, ASR490 appears to be a potent agent that can inhibit Notch1 signaling in colorectal cancer.

Notch Signaling and the Breast Cancer Microenvironment

Notch promotes breast cancer progression through tumor initiating cell maintenance, tumor cell fate specification, proliferation, survival, and motility. In addition, Notch is recognized as a decisive mechanism in regulating various juxtacrine and paracrine communications in the tumor microenvironment (TME). In this chapter, we review recent studies on stress-mediated Notch activation within the TME and sequelae such as angiogenesis, extracellular matrix remodeling, changes in the innate and adaptive immunophenotype, and therapeutic perspectives.

Notch Signaling in Breast Cancer: A Role in Drug Resistance

Breast cancer is a heterogeneous disease that can be subdivided into unique molecular subtypes based on protein expression of the Estrogen Receptor, Progesterone Receptor, and/or the Human Epidermal Growth Factor Receptor 2. Therapeutic approaches are designed to inhibit these overexpressed receptors either by endocrine therapy, targeted therapies, or combinations with cytotoxic chemotherapy. However, a significant percentage of breast cancers are inherently resistant or acquire resistance to therapies, and mechanisms that promote resistance remain poorly understood. Notch signaling is an evolutionarily conserved signaling pathway that regulates cell fate, including survival and self-renewal of stem cells, proliferation, or differentiation. Deregulation of Notch signaling promotes resistance to targeted or cytotoxic therapies by enriching of a small population of resistant cells, referred to as breast cancer stem cells, within the bulk tumor; enhancing stem-like features during the process of de-differentiation of tumor cells; or promoting epithelial to mesenchymal transition. Preclinical studies have shown that targeting the Notch pathway can prevent or reverse resistance through reduction or elimination of breast cancer stem cells. However, Notch inhibitors have yet to be clinically approved for the treatment of breast cancer, mainly due to dose-limiting gastrointestinal toxicity. In this review, we discuss potential mechanisms of Notch-mediated resistance in breast cancer cells and breast cancer stem cells, and various methods of targeting Notch through γ-secretase inhibitors, Notch signaling biologics, or transcriptional inhibitors. We also discuss future plans for identification of novel Notch-targeted therapies, in order to reduce toxicity and improve outcomes for women with resistant breast cancer.

Tamoxifen Downregulates the Expression of Notch1 and DLL1 Genes in MKN-45 Gastric Cancer Cells

PURPOSE

Gastric cancer is one of the most prevalent cancers worldwide and the second most common cause for cancer associated mortality. Anti-tumor effects of tamoxifen in breast cancer are well-established. However, no study has so far investigated the effects of tamoxifen on gene expression of Notch1 and DLL1 in gastric cancer cell line. The present study was conducted to explore the effects of tamoxifen, as a repurposed drug, on gene expression of Notch1 and DLL1 in MKN-45, a gastric cancer cell line.

METHODS

MKN-45 cells were cultured in DMEM/F12 medium containing 10% FBS. Cytotoxic effects of tamoxifen on these cells at various concentrations were evaluated by trypan blue exclusion assay. For gene expression analysis, the cells were first incubated with 100 μM tamoxifen followed by total RNA extraction from treated and control cells. Then, cDNA was synthesized. Quantitative real-time PCR using specific primers for Notch1 and DLL1 was performed to assess the effect of tamoxifen on the transcript of them.

RESULTS

Treatment with tamoxifen decreased viability of MKN-45 cells in a dose-dependent manner. CC₅₀ was estimated to be around 200 μM. Also, tamoxifen at the dose of 100 μM could significantly downregulate mRNA levels of both Notch1 and DLL1 genes as compared with untreated cells by 24% and 92%, respectively.

CONCLUSION

Based on these results, tamoxifen interferes with Notch signaling pathway through downregulating the expression of Notch1 and DLL1 genes and this could be regarded as a mechanism for its anti-cancer effects in this malignant disease.

DAXX-inducing phytoestrogens inhibit ER+ tumor initiating cells and delay tumor development

Recurrence of estrogen receptor (ER)-positive breast tumors despite curative-intent adjuvant therapy is thought to be due to enrichment of tumor initiating cells (TIC) during endocrine therapy (ET). Recently, it was identified that by antagonizing the ER, ET promotes rapid degradation of the death-associated factor 6 (DAXX) protein, which is necessary and sufficient to potently inhibit TICs. Thus, the goal of the current study was to identify a DAXX-inducing agent to inhibit TICs and prevent proliferation of the tumor. Phytoestrogens (naringenin, resveratrol, genistein, apigenin, and quercetin) were screened for DAXX protein expression, anti-TIC and anti-proliferative efficacy in vitro and in vivo. Specific DAXX-inducing phytoestrogens were tested to assess selectivity towards ERα and/or ERβ. Results showed that phytoestrogens tested induced DAXX protein expression and inhibited survival of TICs from ER+ MCF-7 and T47D cells. Only naringenin, resveratrol, and quercetin did not stimulate total cell proliferation. Naringenin, resveratrol, but not quercetin inhibited survival of TICs in vitro and in vivo in a DAXX-dependent manner. Naringenin-induced DAXX protein expression and inhibition of TICs seemed to be more selective towards ERβ while resveratrol was more selective through ERα. Naringenin or resveratrol inhibited the rate of tumor initiation and rate of tumor growth in a DAXX-dependent manner. These results suggest that a therapeutic approach using a phytoestrogen to induce DAXX protein expression could potently inhibit TICs within a tumor to delay or prevent tumor initiation. Therefore, a DAXX-promoting phytoestrogen should be explored for prevention of tumor progression in advanced disease and relapse in the adjuvant setting.

The oncogenic role of Jagged1/Notch signaling in cancer

Aberrant activation of Notch signaling plays an oncogenic role in cancer development. Jagged1 (JAG1) is an important Notch ligand that triggers Notch signaling through cell-cell interactions. JAG1 overexpression has been reported in many different types of cancer and correlates with a poor clinical prognosis. JAG1/Notch signaling controls oncogenic processes in different cell types and cellular contexts. Furthermore, JAG1/Notch signaling cascades activate a number of oncogenic factors that regulate cellular functions such as proliferation, metastasis, drug-resistance, and angiogenesis. To suppress the severe toxicity of pan-Notch inhibitors, JAG1 is attracting increasing attention as a source of therapeutic targets for cancers. In this review, the oncogenic role of JAG1/Notch signaling in cancer is discussed, as well as implications of strategies to inhibit JAG1/Notch signaling activity.

A Novel Flow Cytometric Assay to Identify Inhibitors of RBPJ-DNA Interactions

Notch signaling is often involved in cancer cell initiation and proliferation. Aberrant Notch activation underlies more than 50% of T-cell acute lymphoblastic leukemia (T-ALL); accordingly, chemicals disrupting Notch signaling are of potential to treat Notch-dependent cancer. Here, we developed a flow cytometry-based high-throughput assay to identify compounds that disrupt the interactions of DNA and RBPJ, the major downstream effector of Notch signaling. From 1492 compounds, we identified 18 compounds that disrupt RBPJ-DNA interactions in a dose-dependent manner. Cell-based assays further revealed that auranofin downregulates Notch-dependent transcription and decreases RBPJ-chromatin interactions in cells. Most strikingly, T-ALL cells that depend on Notch signaling for proliferation are more sensitive to auranofin treatment, supporting the notion that auranofin downregulates Notch signaling by disrupting RBPJ-DNA interaction. These results validate the feasibility of our assay scheme to screen for additional Notch inhibitors and provide a rationale to further test the use of auranofin in treating Notch-dependent cancer.

Top Notch Targeting Strategies in Cancer: A Detailed Overview of Recent Insights and Current Perspectives

Evolutionarily conserved Notch plays a critical role in embryonic development and cellular self-renewal. It has both tumour suppressor and oncogenic activity, the latter of which is widely described. Notch-activating mutations are associated with haematological malignancies and several solid tumours including breast, lung and adenoid cystic carcinoma. Moreover, upregulation of Notch receptors and ligands and aberrant Notch signalling is frequently observed in cancer. It is involved in cancer hallmarks including proliferation, survival, migration, angiogenesis, cancer stem cell renewal, metastasis and drug resistance. It is a key component of cell-to-cell interactions between cancer cells and cells of the tumour microenvironment, such as endothelial cells, immune cells and fibroblasts. Notch displays diverse crosstalk with many other oncogenic signalling pathways, and may drive acquired resistance to targeted therapies as well as resistance to standard chemo/radiation therapy. The past 10 years have seen the emergence of different classes of drugs therapeutically targeting Notch including receptor/ligand antibodies, gamma secretase inhibitors (GSI) and most recently, the development of Notch transcription complex inhibitors. It is an exciting time for Notch research with over 70 cancer clinical trials registered and the first-ever Phase III trial of a Notch GSI, nirogacestat, currently at the recruitment stage.

Notch Signaling Pathway and Endocrine Resistance in Breast Cancer

Nearly 70% of breast cancers express the estrogen receptor (ER) and are hormone-dependent for cell proliferation and survival. Anti-estrogen therapies with aromatase inhibitors (AIs), selective estrogen receptor modulators (SERMs) or selective estrogen receptor down regulators (SERDs) are the standard endocrine therapy approach for ER positive breast cancer patients. However, about 30% of patients receiving endocrine therapy will progress during the therapy or become endocrine resistance eventually. The intrinsic or acquired endocrine resistance has become a major obstacle for endocrine therapy. The mechanism of endocrine resistance is very complicated and recently emerging evidence indicates dysregulation of Notch signaling pathway contributes to endocrine resistance in breast cancer patients. The potential mechanisms include regulation of ER, promotion of cancer stem cell (CSC) phenotype and mesenchymal cell ratio, alteration of the local tumor microenvironment and cell cycle. This review will summarize the latest progress on the investigation of Notch signaling pathway in breast cancer endocrine resistance.

P2Y2R has a significant correlation with Notch-4 in patients with breast cancer

Our previous study found that highly metastatic breast cancer cells, such as MDA-MB-231 cells, release higher levels of ATP and exhibit greater P2Y₂ receptor (P2Y₂R) activity than lowly metastatic breast cancer cells, and that P2Y₂R activation mediated by ATP plays a significant role in tumor progression and metastasis. In addition, we reported that radiotherapy-resistant (RT-R) breast cancer cells promote invasion and tumor growth through the activation of P2Y₂R by ATP released from RT-R-breast cancer cells than breast cancer cells. Moreover, increased numbers of cancer stem cells (CSCs) were observed among the RT-R-breast cancer cell population. Therefore, in this study, we investigated the expression level of five CSC markers (CD24, CD44, Oct3/4, Notch-4 and ALDH1A1) as well as P2Y₂R in the tumor tissues of patients with breast cancer and determined which CSC marker correlates with P2Y₂R in breast cancer. According to the immunohistochemical analysis, CD44, Oct3/4 and Notch-4 but not ALDH1A1 were significantly expressed in the tumor tissues (n=180) compared with the normal epithelial tissues (n=20) of patients with breast cancer. It was demonstrated that P2Y₂R expression was increased in tumor tissues of patients with breast cancer compared with normal epithelial tissue. Notably, it was identified that P2Y₂R expression has a significant correlation with only the CSC marker Notch-4 in patients with breast cancer. The results of this study suggested for the first time to the best of our knowledge that Notch-4 has a notable correlation with P2Y₂R, which has important roles in tumor progression and metastasis.

The cross-talk of NOTCH and GSK-3 signaling in colon and other cancers

The GSK-3 kinases, GSK-3α and GSK-3β, have a central role in regulating multiple cellular processes such as glycogen synthesis, insulin signaling, cell proliferation and apoptosis. GSK-3β is the most well studied, and was originally described for its role in regulating glycogen synthase. GSK-3β has been studied as a participant in the oncogenic process in a variety of cancers due to its intersection with the PTEN/PI3K/AKT and RAS/RAF/MEK/ERK pathways. Dysregulated signaling through the Notch family of receptors can also promote oncogenesis. Normal Notch receptor signaling regulates cell fate determination in stem cell pools. GSK-3β and Notch share similar targets such β-catenin and the WNT pathway. WNT and β-catenin are involved in several oncogenic processes including those of the colon. In addition, GSK-3β may directly regulate aspects of Notch signaling. This review describes how crosstalk between GSK-3β and Notch can promote oncogenesis, using colon cancer as the primary example.

A Noncanonical Role of Fructose-1, 6-Bisphosphatase 1 Is Essential for Inhibition of Notch1 in Breast Cancer

Breast cancer is a leading cause of death in women worldwide, but the underlying mechanisms of breast tumorigenesis remain unclear. Fructose-1, 6-bisphosphatase 1 (FBP1), a rate-limiting enzyme in gluconeogenesis, was recently shown to be a tumor suppressor in breast cancer. However, the mechanisms of FBP1 as a tumor suppressor in breast cancer remain to be explored. Here we showed that FBP1 bound to Notch1 in breast cancer cells. Moreover, FBP1 enhanced ubiquitination of Notch1, further leading to proteasomal degradation via FBXW7 pathway. In addition, we found that FBP1 significantly repressed the transactivation of Notch1 in breast cancer cells. Functionally, Notch1 was involved in FBP1-mediated tumorigenesis of breast cancer cells in vivo and in vitro. Totally, these findings indicate that FBP1 inhibits breast tumorigenesis by regulating Notch1 pathway, highlighting FBP1 as a potential therapeutic target for breast cancer. IMPLICATIONS: We demonstrate FBP1 as a novel regulator for Notch1 in breast cancer.

Genetic Profiling of Breast Cancer with and Without Preexisting Metabolic Disease

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer death among women. Various mechanisms are involved in the initiation and progression of breast cancer. Metabolic dysregulation has been associated with increasing breast cancer incidence and mortality. However, little is known about how metabolic disease regulates the development and progression of breast cancer at the molecular level. Here, using a hybridization capture-based panel including 124 cancer-associated genes, we performed targeted next-generation sequencing of tumor tissues and matched blood samples from 20 postmenopausal patients with primary breast cancer, in which 6 cases suffered from preexisting metabolic disorders including hypertension, type 2 diabetes, and coronary heart disease. We took only the protein-altering variants and identified 170 somatic mutations of 59 genes. Among these, 40 mutated genes were found in the metabolic disease group, and 33 mutated genes were found in the non-metabolic disease group. Importantly, nonsynonymous mutations of 26 genes (MSH3, BRAF, MLH3, MTOR, DDR2, ALK, etc.) were uniquely present in the metabolic disease group. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were performed to investigate biological functions and key pathways of somatic mutations. TP53, PIK3CA, and PTEN were the top three commonly mutated genes at a higher frequency compared with the Cancer Genome Atlas (TCGA) data, and several novel but infrequent mutations in other genes were also found. Although further studies are required to validate these variants, our results are the first to suggest a specific molecular profile of breast cancer with preexisting metabolic disease.

Molecular Signaling Regulating Endometrium-Blastocyst Crosstalk

Implantation of the embryo into the uterine endometrium is one of the most finely-regulated processes that leads to the establishment of a successful pregnancy. A plethora of factors are released in a time-specific fashion to synchronize the differentiation program of both the embryo and the endometrium. Indeed, blastocyst implantation in the uterus occurs in a limited time frame called the "window of implantation" (WOI), during which the maternal endometrium undergoes dramatic changes, collectively called "decidualization". Decidualization is guided not just by maternal factors (e.g., estrogen, progesterone, thyroid hormone), but also by molecules secreted by the embryo, such as chorionic gonadotropin (CG) and interleukin-1β (IL-1 β), just to cite few. Once reached the uterine cavity, the embryo orients correctly toward the uterine epithelium, interacts with specialized structures, called pinopodes, and begins the process of adhesion and invasion. All these events are guided by factors secreted by both the endometrium and the embryo, such as leukemia inhibitory factor (LIF), integrins and their ligands, adhesion molecules, Notch family members, and metalloproteinases and their inhibitors. The aim of this review is to give an overview of the factors and mechanisms regulating implantation, with a focus on those involved in the complex crosstalk between the blastocyst and the endometrium.

N3ICD with the transmembrane domain can effectively inhibit EMT by correcting the position of tight/adherens junctions

EMT allows a polarized epithelium to lose epithelial integrity and acquire mesenchymal characteristics. Previously, we found that overexpression of the intracellular domain of Notch3 (N3ICD) can inhibit EMT in breast cancer cells. In this study, we aimed to elucidate the influence of N3ICD or N3ICD combined with the transmembrane domain (TD+N3ICD) on the expression and distribution of TJs/AJs and polar molecules. We found that although N3ICD can upregulate the expression levels of the above-mentioned molecules, TD+N3ICD can inhibit EMT more effectively than N3ICD alone. TD+N3ICD overexpression upregulated the expression of endogenous full-length Notch3 and contributed to correcting the position of TJs/AJs molecules and better acinar structures formation. Co-immunoprecipitation results showed that the upregulated endogenous full-length Notch3 could physically interact with E-ca in MDA-MB-231/pCMV-(TD+N3ICD) cells. Collectively, our data indicate that overexpression of TD+N3ICD can effectively inhibit EMT, resulting in better positioning of TJs/AJs molecules and cell-cell adhesion in breast cancer cells. Abbreviations: EMT: Epithelial-mesenchymal transition; TJs: Tight junctions; AJs: Adherens junctions; aPKC: Atypical protein kinase C; Crb: Crumbs; Lgl: Lethal (2) giant larvae; LLGL2: lethal giant larvae homolog 2; PAR: Partitioning defective; PATJ: Pals1-associated TJ protein.

The Exosome And Breast Cancer Cell Plasticity

Cancer cell plasticity is the ability of cancer cells to reversibly interchange between distinct cell status, which plays a key role in cancer progression. Cancer cell plasticity is now known to be shaped by the secreted nanoparticles termed exosomes which transport proteins and lipids as well as nucleic acids. These aspects have emerged as key determinants of tumor progression and targeting, with approaches such as immunotherapy showing promise in the clinic. While significant strides have been made in this research area, some very interesting questions still warrant more and deeper investigation. We provide a review of the interplay between exosomes and breast cancer cell plasticity, and the potential implication in metastases and drug-resistance.